diff --git a/weed/storage/needle_map/memdb.go b/weed/storage/needle_map/memdb.go
index d3d47b605..fb3d0130d 100644
--- a/weed/storage/needle_map/memdb.go
+++ b/weed/storage/needle_map/memdb.go
@@ -1,9 +1,11 @@
 package needle_map
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"os"
+	"sort"
 
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/iterator"
@@ -34,7 +36,6 @@ func NewMemDb() *MemDb {
 }
 
 func (cm *MemDb) Set(key NeedleId, offset Offset, size Size) error {
-
 	bytes := ToBytes(key, offset, size)
 
 	if err := cm.db.Put(bytes[0:NeedleIdSize], bytes[NeedleIdSize:NeedleIdSize+OffsetSize+SizeSize], nil); err != nil {
@@ -76,6 +77,31 @@ func doVisit(iter iterator.Iterator, visit func(NeedleValue) error) (ret error)
 	return nil
 }
 
+func (cm *MemDb) AscendingVisitByOffset(visit func(NeedleValue) error) (ret error) {
+	var needles []NeedleValue
+	err := cm.AscendingVisit(func(value NeedleValue) error {
+		needles = append(needles, value)
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	sort.Slice(needles, func(i, j int) bool {
+		i_bytes := make([]byte, OffsetSize)
+		j_bytes := make([]byte, OffsetSize)
+		OffsetToBytes(i_bytes, needles[i].Offset)
+		OffsetToBytes(j_bytes, needles[j].Offset)
+		return bytes.Compare(i_bytes, j_bytes) < 0
+	})
+	for _, needle := range needles {
+		ret = visit(needle)
+		if ret != nil {
+			return ret
+		}
+	}
+	return nil
+}
+
 func (cm *MemDb) AscendingVisit(visit func(NeedleValue) error) (ret error) {
 	iter := cm.db.NewIterator(nil, nil)
 	if iter.First() {
@@ -122,7 +148,7 @@ func (cm *MemDb) SaveToIdx(idxName string) (ret error) {
 		idxFile.Close()
 	}()
 
-	return cm.AscendingVisit(func(value NeedleValue) error {
+	return cm.AscendingVisitByOffset(func(value NeedleValue) error {
 		if value.Offset.IsZero() || value.Size.IsDeleted() {
 			return nil
 		}